During an oocyte retrieval procedure, a relatively long aspiration cannula may be inserted into a patient so that the distal end of the cannula is in contact with a patient's ovary. The objective is to puncture an individual follicle in the ovary and withdraw oocytes through the aspiration cannula. Generally the proximal end of the cannula is connected to flexible tubing, which is in turn connected to both a test tube and via the test tube to a vacuum source. The vacuum source provides suction via the test tube to the cannula to allow aspiration of the oocyte from the follicle. In some medical procedures to retrieve oocytes, the physician may puncture several follicles in turn to abstract oocytes from each without removal of the aspiration cannula from the patient.
Several different cannula styles are currently used for oocyte retrieval. One style is a single lumen device. This style requires that any irrigation to assist with the removal of an oocyte be conducted through the same fluid path or lumen that is used for aspiration. In such instances if an oocyte is lodged in the fluid path of the cannula the oocyte may be actually flushed back into the follicle during the irrigation procedure. Therefore the use of a single lumen may create the potential of losing the oocyte during the irrigation procedure. Accordingly, some physicians prefer the use of a dual lumen device for oocyte collection procedures. A dual lumen device has a first fluid path or lumen for aspiration and a second fluid path for irrigation or flushing. The use of separate paths thereby reduces the possibility of flushing an oocyte out of the aspiration path during an irrigation or flushing procedure.
Each oocyte is located in a fluid filled cyst or follicle. Before an oocyte can be retrieved, a physician needs to be able to accurately puncture each cyst prior to retrieval without damaging or losing the oocyte. In order to cleanly puncture the cyst, oocyte collection devices include a cannula having a sharpened bevelled tip. Ideally, the tip is gently inserted into the follicle to puncture the cyst and allow aspiration of the follicular contents. This releases the oocytes. This procedure can take some time, at least several minutes, for instance. During this period the needle or cannula could contain part or all of the follicular contents potentially containing one or more oocytes.
Studies have shown that irreparable damage can occur to an oocyte and particularly its meiotic spindle (or metaphase plate) when subjected to temperatures as little as 4° C. below the ideal of 37° C. This can result in fertilised oocytes having reduced viability even though there is no visible spindle damage. Higher temperatures may also damage an oocyte. Flushing medium held in the relatively long aspiration cannula can cool to an unacceptable degree while a physician is locating and puncturing a follicle and this cooler medium may cause damage to the oocyte.
To assist with insertion of the aspiration cannula an ultrasonic probe may be used. Where the oocyte recovery is done transvaginally a transvaginal ultrasonic probe may be used. The transvaginal ultrasonic probe has a needle guide associated with it and is used to support and aim the needle towards a follicle of an ovary after the transvaginal ultrasonic probe has been inserted into the vagina. The physician then advances the needle through the wall of the vagina into the ovary.
It is the object of this invention to provide a solution to this problem or to at least provide a physician with a useful alternative.
Throughout this specification the term distal is used to indicate that portion of the apparatus, that in use, is further away from the physician and the term proximal is used to indicate that portion of the apparatus, that in use, is nearer to the physician.